1. Field of the Invention
The present invention relates to a structure of the front portion of a vehicle body for an automotive vehicle and, more particularly, to a front body structure of an automotive vehicle body in which an engine mounting structure is reinforced.
Typically, front bodies of an automotive vehicle include a pair of, or right and left, front wheel housings, a pair of, or right and left, front suspension towers, each front suspension being secured to the front wheel housing tower, and a pair of, or right and left, front side frames, each front side frame extending in a lengthwise direction of the vehicle body and being secured to a lower portion of the front wheel housing. In such a front body structure, a plurality of mounting brackets mount a power-plant, including at least an engine and a transmission, in the engine room. One of the plurality of mounting brackets is provided in association either with the front wheel housing or with the front side frame close to the front wheel housing. If the front wheel housing has a mounting bracket attached to it, a portion of the front wheel housing where the mounting bracket is attached must be structurally reinforced. In order for the front wheel housing to reinforce the mounting portion, it is typical to provide a reinforcement primarily welded to the portion of the front wheel housing and secondarily welded to the front side frame and a suspension tower at its lower and upper portions, respectively. Such a front body structure is known from, for instance, Japanese Unexamined Utility Model Publication No. 62-52081.
2. Description of Related Art
Upon a front end collision of an automotive vehicle, impact load acting on the power-plant is applied to the front wheel housing through the mounting bracket. If the mounting portion of the front wheel housing is over-reinforced in structural strength, the impact load is transmitted to front pillars and a cowl of the front body through a suspension tower and a wheel apron reinforcement via a mounting bracket. As a result, the front body is subjected to an decrease in the certainty with which a front wind-shield glass is held. On the other hand, if the mounting portion of the front wheel housing is insufficiently reinforced in structural strength, it allows the power-plant to move backward to a large extent during a front end collision. This also adversely affects to the cowl and a dash-board of the front body, thereby lowering the certainty with which the front wind-shield glass is held.
In particular, since front drive automotive vehicles have a power-plant with a crankshaft oriented in a transverse direction of its front body, an interference between the power-plant and either one of the front side frames is easily caused. In such an automotive vehicle, in order to avoid such an interference, the front side frame is formed with a cut-away portion opening to the outside of the front body for defining a space in which the power-plant can move during a front end collision. If a decrease in structural strength of the front side frame due to the cut-away portion is improperly or insufficiently compensated, the front side frame may possibly be deformed or bent upward at the cut-away portion due to an impact load acting thereon during the front end collision. This deformation affects the front pillars and the cowl of the front body, so as also to decrease the certainty with which the front wind shield glass is held.
For instance, as is well known from, for instance, Japanese Unexamined Patent Publication No. 63-145124, to mount a power-plant in the front body, mounting means are used, through which the power-plant is supported, at its opposite sides, by the front side frames extending in the length wise direction on opposite sides of the front body and at its front and rear ends by a center member extending in the lengthwise direction below the power-plant. When an automotive vehicle having a power-plant thus mounted therein undergoes a front end crash and, as a result, the center member, which mounts the power-plant thereon, deforms downward at its center portion, the power-plant will sink down. This causes rearward movement of the upper portion of the power-plant to be difficult.
For "midship" type automotive vehicles, it is a recent tendency to support the power-plant at its rear end portion by a rigid structural member, different from the center member, through a mounting means for space efficiency. In such a front body structure, in which the power-plant is supported at its rear end portion by a rigid structural member different from a center member, it is difficult to deform the rigid structural member upon a front end collision of the automotive vehicle. Consequently, the power-plant tends to turn upward about a mounting portion of the power-plant, at which a rear end of the power-plant is supported by the rigid structural member, as the center member supporting a front end portion of the power-plant bends or deforms downward during a front end collision. In addition, when the front side frame deforms upward during a front end collision, the power-plant tends to move upward. Such a movement of the power-plant causes an interference of the upper portion of the power-plant with a portion of the front body where a dash panel, for dividing an engine room and a passenger compartment, and a front wind-shield glass are connected.